Marie Foy decided to get tested for the BRCA2 gene mutation that her mother and sister have because she didn’t want to go through life wondering. After learning she had the mutation, she opted for prophylactic surgery to reduce her risk of cancer.

Then her younger sister tested positive for the same genetic mutation that led to their mother's ovarian and breast cancers.

"I started getting nervous," the Wesley Chapel woman recalls. "I said, maybe I should do this."

Eight months later she worked up the courage to see if she shared the BRCA2 gene mutation with her mother and sister. In 2006, Foy was tested at Moffitt Cancer Center in Tampa and discovered she had the same trait.

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The BRCA1 and BRCA2 genes belong to a class of genes known as tumor suppressors. Certain mutations on those genes are associated with significantly increased risk of breast, ovarian and possibly other cancers including colon, pancreatic and prostate.

Patients simply give blood for the test; the process is more complicated from there. Dr. Tuya Pal, a genetics specialist at Moffitt, says to think of the genes as a set of encyclopedias. "You're looking for a spelling mistake in the entire set of encyclopedias," says Pal.

Women who have harmful mutations in either BRCA gene have an average 60 percent chance of developing breast cancer and a 15 to 40 percent chance of developing ovarian cancer in their lifetimes, according to the National Cancer Institute. Without the mutation, women have, on average, about a 12 percent chance of breast cancer and a 1.4 percent chance of ovarian cancer.

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Counseling is essential before and after testing to help patients process the news and decide what to do next.

Foy didn't like her odds. She quickly decided to have a hysterectomy as a precaution against ovarian cancer. The next decision was more agonizing: Should she, like a growing number of high-risk women, have a prophylactic bilateral mastectomy — both breasts surgically removed — to guard against breast cancer?

"It was really, really hard," says Foy, who is 53, married and has no children. "I just thought, I'm going to get this cancer. And I really didn't want to. I didn't want to go through that."

In 2007 Foy had a total hysterectomy and in 2008 she had a bilateral mastectomy with breast reconstruction.

Foy's sister, who is 50 and lives in New York, has declined preventive surgery, sticking with regular screenings since testing positive for the mutation.

Another option for women who test positive for a mutation is chemoprevention, the use of drugs like tamoxifen and raloxifene to prevent cancer.

Risk avoidance is particularly important. The greatest risk for cancer is age, and there's nothing you can do about that. But avoiding smoking and obesity and getting regular exercise are lifestyle measures widely recommended for all women to prevent breast and ovarian cancers.

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Foy's brother, who is 45 and lives in the Tampa Bay area, tested positive for the mutation five years ago.

Although the mutation isn't as firmly linked with colon cancer as it is with breast and ovarian cancers, some studies have suggested a relationship. So Foy's brother immediately insisted on a colonoscopy, a test that usually isn't given until age 50.

Doctors found a malignant tumor, the size of a golf ball. Genetic testing "saved my brother's life," Foy says. "He wasn't supposed to begin screening for 10 more years. The doctor said he would have been dead."

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Most people don't have the genetic mutations. Overall, BRCA1 and BRCA2 mutations account for an estimated 5 to 10 percent of breast cancers and 10 to 15 percent of ovarian cancers among white women in the United States, according to the National Cancer Institute.

So, who should be tested?

Personal and family history of early onset breast cancer (age 50 or younger) or ovarian cancer at any age, especially if it's in a mother, daughter or sister, are among the factors to consider, Pal said. Men with a strong family history such as Foy's may also wish to be tested, both for their personal cancer risk and because — like women — they can pass it along to their children.

Ethnic origin can also be a factor. For instance, BRCA mutations are about five times more frequent in people of Ashkenazi Jewish descent than average.

BRCA isn't the only gene in which mutations lead to cancer, but it's the most common one. In Foy's case, doctors knew where to look because her mother had had extensive testing.

That fact kept her cost down — she paid $300 out of pocket because she didn't want her insurance carrier to know about it.

But in 2008, two years after she was tested, the Genetic Information Nondiscrimination Act was passed. The act, which went into effect in 2009, protects Americans from discrimination by employers or health insurers because of genetic testing.

Earlier this year, a study was published showing that breast and ovarian cancer risk is greatly reduced among women with a genetic mutation who have preventive surgery. It's never zero, however, because it's not possible to remove every trace of tissue.

Foy has no regrets about her decision to have genetic testing and prophylactic surgery to lower her risk of cancer.

"I feel so much better," she says. "I don't have the worries that I used to have."